Process to preserve isopipe during coupling

Abstract

Methods for reducing stress on an isopipe during manufacture of a drawn glass sheet are disclosed including a method comprising providing an isopipe having a root, heating the isopipe to a predetermined temperature, maintaining the isopipe at the predetermined temperature for a period of time sufficient to relieve at least a portion of a tensile stress on the isopipe root, coupling the isopipe to a down-comer, and then providing glass to the isopipe. Also disclosed is a method comprising heating an isopipe such that the temperature difference between the weir and the root of the isopipe, after heating and prior to coupling, is less than about 100° C. A method comprising application of a compressive force to the ends of an isopipe root during heating is also disclosed.

1. A method for reducing stress on an isopipe during manufacture of a drawn glass sheet, the method comprising:
 a) providing an isopipe having a weir and a root; 
 b) positioning the isopipe within a muffle of a sheet glass manufacturing system; 
 c) heating the isopipe to a predetermined temperature wherein the predetermined temperature is from about 800° C. to about 1,250° C.; 
 d) maintaining the isopipe at the predetermined temperature for a period of time sufficient to relieve at least a portion of a tensile stress on the isopipe root wherein the period of time is at least about 10 hours; 
 e) after step d), coupling the isopipe to a down-comer; and 
 f) after step e), providing glass to the isopipe. 
 
     
     
       2. The method of  claim 1 , wherein the period of time is at least about 20 hours. 
     
     
       3. The method of  claim 1 , wherein the period of time is at least about 30 hours. 
     
     
       4. The method of  claim 1 , wherein the tensile stress is after the period of time is less than about 1,000 psi. 
     
     
       5. The method of  claim 1 , wherein the tensile stress after the period of time is at least about 500 psi less than the tensile stress prior to the period of time. 
     
     
       6. The method of  claim 1 , wherein the tensile stress after the period of time is at least about 800 psi less than the tensile stress prior to the period of time. 
     
     
       7. The method of  claim 1 , wherein a compressive force is applied to the isopipe root at least during step b). 
     
     
       8. The method of  claim 7 , wherein after step c) and prior to step d), the weir and the root have a temperature difference of less that about 100° C. 
     
     
       9. The method of  claim 1 , wherein a compressive force is applied to the isopipe root at least during step c). 
     
     
       10. The method of  claim 9 , wherein after step c), and prior to step d), the weir and the root have a temperature difference of less than about 100° C. 
     
     
       11. The method of  claim 1 , wherein after step c) and prior to step d), the weir and the root have a temperature difference of less than about 100° C. 
     
     
       12. A method for reducing stress on an isopipe during manufacture of a drawn glass sheet, the method comprising:
 a) providing an isopipe having a weir and a root; 
 b) positioning the isopipe within a muffle of a sheet glass manufacturing system; 
 c) heating the isopipe to a predetermined temperature wherein the predetermined temperature is from about 800° C. to about 1,250° C.; 
 d) after step c), coupling the isopipe to a down-comer; and 
 e) after step d), providing glass to the isopipe; 
 wherein after heating and prior to coupling, the weir and the root have a temperature difference of less than about 100° C. 
 
     
     
       13. The method of  claim 12 , wherein after heating, the weir and the root have a temperature difference of less than about 75° C. 
     
     
       14. The method of  claim 12 , wherein a compressive force is applied to the isopipe root at least during step b). 
     
     
       15. The method of  claim 12 , wherein after step b) and before step c), further comprising the step of maintaining the isopipe at the predetermined temperature for a period of time sufficient to relieve at least a portion of a stress on the isopipe. 
     
     
       16. A method for reducing stress on an isopipe during manufacture of a drawn glass sheet, the method comprising:
 a) providing an isopipe having a weir and a root; 
 b) positioning the isopipe within a muffle of a sheet glass manufacturing system; 
 c) heating the isopipe to a predetermined temperature wherein the predetermined temperature is from about 800° C. to about 1,250° C.; 
 d) after step c), coupling the isopipe to a down-comer; and 
 e) after step d), providing glass to the isopipe; 
 wherein during heating and prior to coupling, a compressive force sufficient to relieve at least a portion of a tensile stress on the isopipe is applied to the root, and 
 wherein after step c) and before step d), further comprising the step of maintaining the isopipe at the predetermined temperature for a period of time sufficient to relieve at least a portion of the tensile stress on the isopipe wherein the period of time is at least about 10 hours. 
 
     
     
       17. The method of  claim 16 , wherein the compressive force is less than about 1,000 lb. 
     
     
       18. The method of  claim 16 , wherein the compressive force is at least about 2,500 lb.